The structure disclosed in Japanese Patent Application Publication No. 60-15510 is known as an example of a conventional vehicle body front structure at rear portions of front side members.
As illustrated in FIG. 29, in this vehicle body front structure, a cowl 70 of a vehicle body is locally expanded in a truncated pyramid shape to thereby form a base body 72 having a stable configuration and a large supporting capacity. Further, a front side member 74 is bifurcated by a bifurcating beam 76 fitted thereon before contacting the base body 72 having a stable configuration. At this time, a total of three arms 78, 80, 82 are formed. These arms surround at least one portion of the base body 72 having a stable configuration, so as to introduce the generated force proportionally. Further, the arm 78 ends in an inner tunnel wall 86 within the range of a longitudinal central axis 84 of the vehicle, and the arm 80 is supported on a front pillar 88. Further, the other arm 82 is obtained by extending the front side member 74, and is joined to a lower portion floor 92 and extends up to a sill 94 without interrupting transmission of a force.
Consequently, the impact force on the front side member 74 is supported by the inner tunnel wall 86, the front pillar 88 and the sill 94, which serve as frame members, via the three arms 78, 80, 82.
However, in this vehicle body front structure, the front side member 74 is crushed to absorb the impact force at the time of a collision, while the three arms 78, 80, 82 suppress the deformation of the vehicle compartment without having the intended impact-absorbing function.
A technique relating to the present invention is described in Japanese Patent Application Laid-Open No. 5-170139 which discloses a vehicle body front structure in which, when a vehicle traveling forward collides, deformation proceeds successively from the front portion toward the rear portion of the vehicle body, and as the deformation proceeds toward the rear portion, the amount of impact energy absorbed increases.